This invention relates to a multi-well filtration device including a filtration membrane on each well which can be removed from the wells for analysis subsequent to filtration.
Test plates for in vitro analysis which contain a multiplicity of individual wells or reaction chambers are commonly known laboratory tools. Such devices have been employed for a wide variety of purposes and assays as exemplified by U.S. Pat. Nos. 3,694,464; 4,304,865; 4,276,048; 4,154,795; 4,427,415; 4,526,690 and Re 30,562. Microporous membrane filters and filtration devices containing such microporous membranes have been especially useful with many of the recently developed cell and tissue culture techniques and assays, particularly those in the field of virology and immunology, wherein the material of interest is retained by the filter. Typically, a ninety-six well filtration plate is used to conduct multiple assays simultaneously, some steps which may last several hours prior to performing filtration. Often the material of interest is retained on the filter. However, if an analytical instrument of interest cannot read the filters directly in the plate wells, the filters must be removed from the wells.
It has also been proposed to utilize a die-punch having a flat face which is inserted into the well and through the filter paper bearing the retentate in order to direct the filter paper and retentate from the well into a vial for subsequent testing. This system has two major problems. First, many times only a portion of the filter paper circumference is sheared and the filter disc remains attached to the well. Secondly, the flat face of the punch tends to remove some of the retentate from the filter paper so that the subsequent testing is inaccurate. An alternative system utilizes a hollow tube as a punch to minimize the contact face of the punch and reduce the amount of sample accidentally transferred to the punch. In another system, the filter is scored about its circumference in order to facilitate subsequent punching. This system is undesirable since accidental rupturing of the filter paper along the scoring can occur. Also, all of these systems are undesirable since they each involve the physical transfer of individual filter discs.
For a counter which requires a flat sample array, it would be preferable to transfer the filter discs directly from the well ends to a film coated with adhesive to maintain the relative locations of all the filter discs. This system is satisfactory with some membrane filters but not with multi layer filter laminates which have a tendency to delaminate thereby effecting transfer of only a portion of the bottom filter layer to the adhesive and leaving the support web and all the upper filter surface and sample still attached to the well. Accordingly, it would be desirable to provide a means for removing retentate and filter paper from a multi-well filtration plate which assures that the filter paper will be completely removed from the well without loss of a portion of the retentate for purposes of subsequent testing. Furthermore, it would be desirable to provide such means which permits removal of the filter and retentate from a plurality of wells simultaneously onto a flat surface so that use of analytical apparatus requiring a flat surface for supporting samples is facilitated.